Alkali Aggregate Reaction-Alkali-Silica reaction in concrete
Subnote
Forward:
1.To ensure durability whether or not, achieved by concrete, certain significant tests though not in general, but, are carried out depending on requirements under specifications.
2.Some of tests that have recently been mandated, is Alkali Silica Reaction while other, is Rapid Chloride Penetration. Laboratory procedures for conducting such tests, are elaborated in testing methods under codes.
3.Just indicative theoretical reference is given herein for certain understanding of what Alkali & Silica in Aggregate, are related to?
4.It is suggested about contents of this sub note being based on collections from experience. Of course, there is no guaranteed certification respecting durability delivery but, code provisions requirements are to be met.
5.Also, experienced during concrete pours & placement that while, using supplementary cementing material as replacement of cement, initial crack formation is prevented to a considerable extent, should adequate initial curing arrangements are resorted to.
6.Though other senior & eminent authors have covered, various aspects relating to this subtopic, yet, it is tried to present a little more.
7.Various cracks were noted during field construction of a sewage treatment plant in gulf that exhibited cracks on walls even, after using 30 % replacement of cement by PFA. Later, size of rebar dia & its spacing were experimentally, altered to prevent cracking formation.
8.It was suggested to representing managers to better use GGBS but, due to some restraints, it was not permitted. Later, it was noticed that surface exhibited certain improvement after reduction of rebar spacing & reducing bar size as well in addition to reducing length of wall panel. It is further added as explained in previous note that GGBS can be controlled to have desired fineness, while PFA not.